Charles
H.
Bennett

Charles H. Bennett was born in 1943, the son of music teachers Anne Wolfe Bennett and Boyd Bennett. He graduated from Croton-Harmon High School in 1960 and from Brandeis University, majoring in chemistry, in 1964. He received his PhD from Harvard in 1971 for molecular dynamics studies (computer simulation of molecular motion) under David Turnbull and Berni Alder, continuing this research as a postdoc under the late Aneesur Rahman at Argonne National Laboratory.

Since coming to IBM Research in 1972, he has worked on various aspects of the relation between physics and information. In 1973, building on the work of IBM's Rolf Landauer, he showed that general-purpose computation can be performed by a logically and thermodynamically reversible apparatus, which can operate with arbitrarily little energy dissipation per step because it avoids throwing away information about past logical states; and in 1982 he proposed the currently accepted resolution of the Maxwell's demon paradox, attributing the demon's inability to violate the Second Law to the thermodynamic cost of destroying, rather than acquiring, information. In collaboration with Gilles Brassard of the University of Montreal he developed a practical system of quantum cryptography, allowing secure communication between parties who share no secret information initially, based on the uncertainty principle instead of usual computational assumptions such as the difficulty of factoring, and with the help of John Smolin built a working demonstration of it in 1989.

Other research interests include algorithmic information theory, in which the concepts of information and randomness are developed in terms of the input/output relation of universal computers, and the analogous use of universal computers to define the intrinsic complexity or "logical depth" of a physical state as the time required by a universal computer to simulate the the evolution of the state from a random initial state. In 1983-5 as visiting professor of computer science at Boston University, he taught courses on cryptography and the physics of computation.

In 1993 Bennett and Brassard, in collaboration with Claude Crepeau, Richard Jozsa, Asher Peres, and William Wootters, discovered "quantum teleportation," an effect in which the complete information in an unknown quantum state is decomposed into purely classical information and purely non-classical Einstein-Podolsky-Rosen (EPR) correlations, sent through two separate channels, and later reassembled in a new location to produce an exact replica of the original quantum state that was destroyed in the sending process. In 1995-7, working with Smolin, Wootters, IBM's David DiVincenzo, and other collaborators, he helped found the quantitative theory of entanglement and introduced several techniques for faithful transmission of classical and quantum information through noisy channels. These techniques, together with quantum teleportation, became the basic building blocks for quantum information processing, and especially fault tolerant quantum computation. In 2001, Bennett and collaborators introduced the notion of entanglement assisted capacity, showing it to be the natural generalization, for quantum channels, of Shannon's channel capacity. More recently they demonstrated the quantum reverse Shannon theorem, according to which, in the presence of appropriate entanglement resources, any two quantum channels can simulate one another efficiently and reversibly.

Beginning in 2006 he became interested in the emergence of classical correlations and computationally complex behavior from quantum laws, arguing that thermal disequilibrium is necessary for this emergence, and that most classical information created on earth, e.g. the pattern of sand grains on a beach, is transient, eventually escaping into space as thermal radiation. In 2009-10 he and coauthors argued that closed timelike curves, if they exist, would have much less ability to speed up hard computations than formerly supposed.

With IBM colleagues DiVincenzo, Linsker, Smolin, and Donkor he devised practical methods using physical interactions to protect audio/visual and other recordings of real-time processes from falsification, pre-, or post-dating.

Bennett is an IBM Fellow, a Fellow of the American Physical Society, and a member of the US National Academy of Sciences. He is a recipient of the Rank Prize, the Harvey Prize, the Okawa Prize, and honorary doctorates from Masaryk University, University of Gdansk, University of Bristol, and ETH-Zurich. He is married with three grown children and seven grandchildren. His wife is retired from having directed a housing mobility program in Yonkers, New York. His main hobbies are photography and music.